Process for making leather with the assistance of iron salts



1,364,316Q No Drawing. Application "filed March'lO, 1917,

UNITED STATES PATENT OFFICE."

OTTO 3615M, OF DARMSTADTQGERMANY.

PROCESS FOR MAKING LEATHER wrrn run ASSISTANCE or neon SALTS.

" .To all whomz't may concern. V

Be it known that I, OTTO RiiHM, a citizen of Germany, residing at No. 46 Weiterstadwith the assistance of ferric iron oxid salts. Heretofore however certaln difficulties arose which prevented the production of a practically useful iron leather. If the salts ar'e too acid the depilated skins are indeed tanned throughout, but the leather is not stable in light and becomes brittle and grain-broken. If basic salts are used, only the outer layers are tanned, while the inner layers are slack tanned, and in this case also the grain breaks.

Now it has been found that with ferric iron oxid salts leather can be made which is stable in water and light and does not become cracked in grain, if previous, or in addition, to the tanning with iron salts, a tanning process is carried out with aldehydes, for example formaldehyde. The iron salts can-be more or less basic or acid, and the leather produced, like alum leather, can be dried acid, or like chrome leather, it-can be'neutralized, before being dried.

The aldehyde tanning moreover renders it possible to incorporate any desired quantity of. iron oxid, up to 30%' and more, in the skin, without the leather losing surface, if, alternately, the iron salts are allowed to act and then ammonia, alkalis and alkaline salts are used for neutralizing. In this way leather of different degrees o'fsoftness or hardness, even to sole leather, can be produced, and the. iron tanned sole leather has,

for example, overchrome tanned leather the advantage that in a wet condition it is not slippery, and therefore does not cause the wearer of the boots to fall, like chrome leather.

Example: 100 partsof depilated skins are worked hour with 200 parts water 5 parts of 40% formaldehyde solution- 2 parts sodium'bicarbonate. The skins are then washed with water and. with basic ferric iron. chlorid in doses the desired quantity of if n has been taken Specificationo'f Letters Patent.

sod

of 1020% until Patented Jan. 4, 1921.

Serial No. 154,033. Renewed May 28, 1920. Serial No. 385,064.

up. As soon as no more iron is taken up by the-depilated skins, they are neutralized with a. 4 This iron aldehyde tanning can be combined with a tanning by phenols, naphthols, aromatic carbon acids and vegetable tanning substances, so that a greater variety of leather can be obtained.

By other substances which yield insoluble compounds with iron the properties of this iron leather may also be modified, for example, by soa'ps, or, with the help of sulfids and sulfur may be incorporated.

Further it has been shown bination of the iron-aldehyde tanmng processes affords a special technical advantage, if, as mentioned in the above example, the process is carried outwith basic ferric iron chlorid. I

The mineral tanned leather heretofore known and used, which has been made either with aluminium or chrome salts has the property that, in addition to the particular IIIGtELlOXIdS, they contain a residue of acids.

that the comv They are compounds of the skin with basic metal salts. For example, chrome leather contains 310% acid, see Jettmar, Hamibuch ale?" Chromgerbung, 1912, page 115. The consequence of this acid residue is that such leather cannot be well used Where it comes into contact with metals, because the metals are oxidized. I

Now the remarkable fact has been dis covered that, basic ferric iron chlorid dissociates entirely in the presence of skin and water, the iron combining with the skin,- so that a leather is obtained which is entirely free from acid. If however depilated skins impregnated in this way-with iron hydroxidare dried gether and do not yield a technically utilizableleather. The leather is however utilizable, if, according to the present invention, before, or after, the treatment with ferric iron chlorid the skins are tanned with formaldehyde. Sheep skins treatedin this. way, for example, yield a perfect substitute for chamois leather.

they will shrink to-v Y in contact with this leather. If, instead of ferric iron chlorid, ferric iron sulfate for example, is used, such neutral leather is not obtained. 7

What I claim and desire to secure by Let-- ters Patent of the United States'is:

1. The process for producing leather which consists in subjecting the skins to the action of aldehydes and ferric iron salts.

2. The process for producing leather which consists in subjecting the skins to the action of formaldehyde and ferric iron salts.

3. The process for producing leather which consists in subjecting the skins to the action of formaldehyde and ferric iron chlorid.

4;. The process for producing leather which consists in subjecting the skins to the simultaneous action of aldehydes and ferric iron salts.

5. The process for producing leather which consists in subjecting the skins to the action of aldehydes and ferric iron salts and subsequently treating the same with alkalis.

6. The process for producing leather which consists in sub'jecting'the skins to the action of aldehydes and ferric iron salts and neutralizing the same with sodium bicarbonate.

7 The process for producing leather which consists in subjecting the skins to the action of a formaldehyde solution and sodium bicarbonate, then tanning said skins with basic ferric iron chlorid and neutralizing with soda, and then repeating the treatment several times with the ferric iron salt and soda. 7

8. The process for producing leather which consists in subjecting the skins to the action of aldehyde and ferric iron salts and then to the action of vegetable tanning sub stances.

OTTO ROHM. 

